The Evolution of Marine Larval Dispersal Kernels in Spatially Structured Habitats: Analytical Models, Individual-Based Simulations, and Comparisons with Empirical Estimates Allison K. Shaw, 1, * Cassidy C. D’Aloia, 2,† and Peter M. Buston 3 1. Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, Minnesota 55108; 2. Woods Hole Oceanographic Institution, Biology Department, Woods Hole, Massachusetts 02543; 3. Boston University, Department of Biology and Marine Program, Boston, Massachusetts 02215 Submitted April 2, 2018; Accepted November 2, 2018; Electronically published January 17, 2019 Online enhancements: appendixes. Dryad data: http://dx.doi.org/10.5061/dryad.s3j9074. abstract: Understanding the causes of larval dispersal is a major goal of marine ecology, yet most research focuses on proximate causes. Here we ask how ultimate, evolutionary causes affect dispersal. Build- ing on Hamilton and May’s classic 1977 article “Dispersal in Stable Habitats,” we develop analytic and simulation models for the evolu- tion of dispersal kernels in spatially structured habitats. First, we inves- tigate dispersal in a world without edges and find that most offspring disperse as far as possible, opposite the pattern of empirical data. Add- ing edges to our model world leads to nearly all offspring dispersing short distances, again a mismatch with empirical data. Adding resource heterogeneity improves our results: most offspring disperse short dis- tances with some dispersing longer distances. Finally, we simulate dis- persal evolution in a real seascape in Belize and find that the simulated dispersal kernel and an empirical dispersal kernel from that seascape both have the same shape, with a high level of short-distance dispersal and a low level of long-distance dispersal. The novel contributions of this work are to provide a spatially explicit analytic extension of Hamil- ton and May’s 1977 work, to demonstrate that our spatially explicit sim- ulations and analytic models provide equivalent results, and to use sim- ulation approaches to investigate the evolution of dispersal kernel shape in spatially complex habitats. Our model could be modified in various ways to investigate dispersal evolution in other species and seascapes, providing new insights into patterns of marine larval dispersal. Keywords: biological oceanography, dispersal kernel, evolutionarily stable strategy, larval dispersal, marine ecology, population connec- tivity. Introduction Understanding the patterns, causes, and consequences of larval dispersal is a major goal of marine ecology and bi- ological oceanography (Cowen et al. 2002; Botsford et al. 2009). Patterns of larval dispersal determine the probabil- ity of larval exchange between populations, which in turn has major consequences for population dynamics (Bots- ford et al. 2001; Hastings and Botsford 2006) and genetic differentiation within metapopulations (Taylor and Hell- berg 2003; D’Aloia et al. 2015). Consequently, dispersal is an important consideration in fisheries management and reserve design (Sala et al. 2002; Sale et al. 2005). Larval dispersal was once assumed to be extensive, lead- ing to demographically and genetically open marine popu- lations (Roughgarden et al. 1985; Scheltema 1986; Roberts 1997). However, interdisciplinary efforts have revealed het- erogeneity among species in the scale of marine dispersal (Kinlan and Gaines 2003). More recently, complete descrip- tions of dispersal patterns have emerged, drawing on ge- netic parentage analysis (D’Aloia et al. 2015; Williamson et al. 2016; Almany et al. 2017) or spatially extensive data on reproduction and settlement (Hameed et al. 2016). Col- lectively, these studies provide evidence that diverse marine species exhibit leptokurtic patterns of dispersal, with a large number of offspring staying relatively close to home and a smaller number of offspring dispersing long distances. The qualitative similarity in these empirical dispersal patterns, for marine species with varied life-history traits and habitat associations, raises the intriguing question of what gener- ates these patterns. Generally, when marine ecologists and biological ocean- ographers consider the causes of variation in patterns of dispersal, they focus on proximate causes such as adult spawning characteristics, larval behavior, larval duration, and oceanographic flow fields (Treml et al. 2015). With * Corresponding author; email: ashaw@umn.edu. † Present address: University of New Brunswick, Department of Biological Sciences, Saint John, New Brunswick E2L 4L5 Canada. ORCIDs: Shaw, http://orcid.org/0000-0001-7969-8365; D’Aloia, http://orcid .org/0000-0002-0824-0151. Am. Nat. 2019. Vol. 193, pp. 424–435. q 2019 by The University of Chicago. 0003-0147/2019/19303-58374$15.00. All rights reserved. DOI: 10.1086/701667 vol. 193, no. 3 the american naturalist march 2019 This content downloaded from 128.128.132.017 on March 26, 2019 12:51:55 PM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).